how do i transfer apps from i pad and i phone to mac air ?

The MacBook Air has a different operating system than the iPad and iPhone -- OS X on the Mac and iOS on the iPad and iPhone. You can't simply transfer an app from one operating system to the other and have it run. Many apps have versions with similar capabilities for each operating system -- Pages for example has both an OS X version and an iOS version.

You can sync many things (e.g. Contacts, calendars, reminders, notes etc) via iCloud by turning on settings in the following:

On the iPhone/iPad: Settings > iCloud

On the Mac: Apple menu > System Preferences > iCloud

You can sync many data files via iCloud Drive: iCloud Drive FAQ - Apple Support

You can sync photos via iCloud Photo Library: iCloud Photo Library - Apple Support

Hi

Just use the same apple ID go to settings on all devices & turn on home sharing

Look at purchases on itunes store bottom right where is says more.

Cheers

Brian

You can transfer purchases, except apps, over to your Mac's iTunes library (e.g. for backup purposes and so that you can sync them to other devices) by connecting them and doing File > Devices > Transfer Purchases. Apps you will have to redownload directly on your Mac's iTunes e.g. via the Account > Purchased menu option - iOS 9 introduced 'app thinning' which allows only what is needed by an app on a particular device to be downloaded onto the device, so you may not have a complete app on your iPad or iPhone (and therefore Transfer Purchases no longer copies apps back).

To sync your iPad and iPhone to your new Mac try the steps on this user-tip : Syncing to a "New" Computer or replacing a "crashed" Hard Drive

Some of the steps on that page have changed slightly (it was written for a previous version of iTunes) :

5, is now File > Devices > Transfer Purchases

6, 'Reset Warnings' at the bottom of the device's Summary tab in iTunes

7, File > Devices > Back Up

8, File > Devices > Restore from Backup (or Restore Backup button on the Summary tab)